Security researchers have spotted the Zeus botnet running an unauthorized command and control center on Amazon's EC2 cloud computing infrastructure.

This marks the first time Amazon Web Services' cloud infrastructure has been used for this type of illegal activity, according to Don DeBolt, director of threat research with HCL Technologies, a contractor that does security research for CA. The hackers didn't do this with Amazon's permission, however. They got onto Amazon's infrastructure by first hacking into a Web site that was hosted on Amazon's servers and then secretly installing their command and control infrastructure.

DeBolt declined to say whose Web site was hacked to get onto Amazon's cloud, but the Zeus software has now been removed, he said. Zeus is a password-stealing botnet. Variants of this malware have been linked to more than US$100 million in bank fraud in the past year.

He thinks the hackers may have just stumbled on a Web site with a security vulnerability -- they may have hacked the site's software or simply stolen an administrative password from a desktop computer to get on the site. "I think it's more a target of opportunity than a target of choice," he said.

In the past few years, law enforcement takedowns and bad publicity have made it harder for many criminals to host their back-end infrastructure in legitimate or even semi-legitimate data centers, so they have moved to Web based services. Although this didn't happen in this case, law enforcement officials worry that criminals might start using stolen credit cards to purchase cloud-based computing services from companies such as Amazon.

In August, security vendor Arbor Networks spotted a botnet that used Twitter to issue commands to hacked computers. Security experts say that criminals will probably seek out new Web services to use in 2010.